具有三核Cd(Ⅱ)簇单元和螺旋链的脯氨酸类单一手性金属-有机框架材料的合成、 结构和性质

在溶剂热反应条件下, 使用含氮辅助配体1,4-二(4-吡啶基)苯(1,4-DPB)和半刚性脯氨酸衍生物配体(R)-5-(2-羧基吡咯烷-1-羰基)间苯二甲酸(R)-H₃PIA]或(S)-5-(2-羧基吡咯烷-1-羰基)间苯二甲酸(S)-H₃PIA]与Cd²⁺构筑了单一手性金属-有机框架材料Cd_1.5((R)-PIA)(1,4-DPB)_1.5]·0.75H₂O·xGuest(1-D)和Cd_1.5((S)-PIA)(1,4-DPB)_1.5]·0.75 H₂O·xGuest(1-L). 配合物1-D和1-L呈具有开放孔道的三维柱层式框架结构, 含有三核镉簇单元 Cd₃(CO₂)₆与两种螺旋链构建的波浪形Cd-PIA层. 分别对上述化合物进行了粉末X射线衍射、 热重分析、 圆二色谱和荧光光谱等测试. 测试结果显示配合物1-D和1-L都是以纯晶体的形式存在, 2种配合物的热失重曲线接近, 圆二色谱有明显的正负吸收峰, 符合其对映体的结构特征.

Syntheses,Structures and Properties of Homochiral Metal-organic Frameworks with Helices and Trinuclear Cluster Units Based on Semirigid Proline Derivatives†

With the help of nitrogen heterocycle auxiliary ligand 1,4-di(pyridin-4-yl)benzene)(1,4-DPB), a pair of homochiral metal-organic frameworks named Cd_1.5((R)-PIA)(1,4-DPB)_1.5]·0.75H₂O·xGuest(1-D) and Cd_1.5((S)-PIA)(1,4-DPB)_1.5]·0.75 H₂O·xGuest(1-L)H₃PIA=5-(2-carboxypyrrolidine-1-carbonyl)isophthalic acid] have been prepared from proline derivative ligands (R)-H₃PIA and (S)-H₃PIA and cadmium ions. Crystallographic analysis indicates that complexes 1-D and 1-L feature three-dimensional open pore structure, containing wavy metal-carboxylate layers and almost linear trinuclear cadmium cluster units. In complexes 1-D and 1-L, the wavy metal-carboxylate layers consists of two types of homochiral helical chains, which are constructed by PIA fragments and cadmium ions. Moreover, powder X-ray diffraction patterns(PXRD), thermogravimetric analysis(TGA), circular dichroism(CD) spectra, and photoluminescent spectra of complexes 1-D and 1-L were also investigated. The results show all the peak positions of simulated and experimental PXRD patterns match well with each other, indicating that the complexes were obtained as a single phase. Furthermore, TGA curves of complexes 1-D and 1-L are very similar to each other and their CD spectrum have obviously positive or negative signal, which accord with their enantiomeric properties.